Sorry to be boring, but FIA thinks it's not safe to put cameras on the helmets, or even on the seats.
This camera angle, attached to the seat, is not allowed anymore: https://www.youtube.com/watch?v=PMIKuS2Bz1k
Also if you think the helmet camera would be streamed online, it means there would have to be a cable attached to it (not just recording on a memory card) which would be another safety issue if the driver has to exit the car quickly.